# Tag Info

4

Your fault attack scenario correspond to this paper : A Differential Attack Technique Against SPN Structures with Application to AES and KHAZAD (Piret & Quisquater - CHES 2003) This paper describe how to retrieve four bytes of the last round key with at least two pairs of ciphertext/faultytext. Each pair of ciphertext $C$ and faultytext $C^*$ could be ...

3

Probably the biggest vulnerability is that the message expansion is too linear. The linearity of the SHA-1 message expansion is why we are able to find such good differential paths. There can be differences at the beginning of the message and by the end of the message expansion they are mostly canceled out.

3

From your picture I deduce that $A$ and $B$ are both 8 bits. So this construction can be seen as a $16 \times 8$ bit S-box (not bijective). The fact that it's not square is probably what is causing confusion. Usually, for SPNs, invertible S-boxes are used. Non-invertible S-boxes are less common, but they certainly have applications. One of the things we can ...

2

"Not vulnerable" is not how I would describe it, but my understanding is that the existing attacks on DES cannot directly not work with 3DES. At the moment, the best attack against single DES is a linear attack which requires $2^{43}$ plaintext-ciphertext pairs, and has a time complexity of at between $2^{39}$ and $2^{43}$ operations. Linear cryptanalysis ...

2

This is known as the "key complementation" property of DES; I had thought that it actually predated Biham and Shamir's work. In any case, your questions: Does this hold for only that particular combination of s box or it will be same for any S-box combination It'd remain even if you change the sbox's arbitrarily. The reason for this is that it is not ...

2

With DES, the issue is the size of the s-box. The DES s-boxes are highly tuned for their security properties, but if you compare their nonlinearity to the larger AES s-box, the are quite inferior. Note than random s-boxes and key dependent s-boxes are not the same thing. Random = fixed random, key dependent = permuted s-boxes based on the key. A random set ...

1

XORing with a key indeed does not change the difference. But usually before the XORing there is nonlinear layer (Sboxes?) which changes the difference. For example $(N rounds...)(Sbox)(AddKey)$. You can use a differential up to the beginning of this layer. Then, for different subkeys you will get same sbox output differences, but the sbox input differences ...

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